Pressure reduction and flow regulation device

Abstract: The invention provides a pressure regulator (1) for low pressure delivery of gases from a high pressure source. The regulator comprises a gas inlet (2) and a gas outlet (3) defining a gas path (4) therebetween. A regulating element (5) is disposed downstream of the inlet and remote from the gas path (4). The device also includes heat exchange means (15) in the form of a powered heater or non-powered ambient heater disposed intermediate the gas inlet (2) and the regulating element (5). The regulating element (5) is resiliently displaceable in response to gas pressure and mechanically connected to operate a valve (6) at the gas inlet (2) to thereby regulate the gas pressure at the gas outlet (3). The regulator of the invention can advantageously be used in a gas distribution system delivering gaseous fumigant from a high pressure source such as a cylinder of fumigant in a liquified CO₂ base, the regulator providing a sensitive and accurate pressure regulation that is more robust and less prone to blockage than most of the prior art devices.

Description: The present invention relates to gas pressure regulators particularly suited for low pressure delivery of liquifiable and permanent gases from a high pressure source. The invention has been developed primarily for the controlled delivery of liquifiable gases or gas mixtures such as CO 2 or CO 2 based preparations, examples of which include CO 2 based pesticidal formulations. However, it will be appreciated that the invention may be used to regulate the delivery of many other types of gases, both liquifiable and non liquifiable. Gaseous pesticidal preparations having a CO 2 base are particularly useful for fumigating grain storage silos. However, numerous problems have been encountered when trying to regulate the delivery of such gas products. One reason is because the product is stored in the liquid state under high pressures of around 5000 kPa and is preferably delivered at a significantly lower delivery pressure of around 10 to 100 kPa. Operational problems are usually encountered when using conventional pressure regulating devices to deliver gaseous products of this kind, particularly with gases such as CO 2 . This is due to the severe pressure and temperature changes that occur on delivery as well as the associated volumetric expansion caused by the resultant gasification of the liquid gas. Whilst the severity of these effects will alter with various gases, they will nonetheless be present in the low pressure delivery of almost any gas from a high pressure source. In the prior art, pressure regulation of such preparations was usually achieved via control valves for high flow rate applications and special purpose regulators for lower flow rate installations. However, neither of these devices are generally able to maintain an even pressure when regulating liquified gases to a gaseous state. In such cases dry ice tends to form at the valve seat causing "spitting" and the output tends to fluctuate wildly due to the large gaseous volume increases and the irregularity of the flow. It should also be noted that the use of control valves with the necessary associated control equipment is a relatively high cost option. Furthermore, as these various prior art regulating devices are usually designed to operate in-line, the componentry of the device is subjected directly to the variations in temperature and volumetric changes referred to above, and as such may have a reduced life span due to these changes. Another problem associated with the regulation and delivery of preparations such as CO 2 based pesticides, is the gradual build-up of resin-like polymer residues which adversely affect the operation of the prior art regulation devices. It should also be noted that regulators used in fumigant delivery systems for dispensing gaseous pesticides of this kind are often required to operate continuously without monitoring for periods in the order of 30 days. Accordingly, safety, reliability and consistency of operation are extremely important. Furthermore, as there is a large market of small farming operations, there is a need for a regulating system that is reliable but not prohibitively expensive. FR-A-870 918 discloses a pressure regulator for low pressure delivery of gas from a high pressure source comprising all the features of the preamble of Claim 1 attached hereto. Unfortunately, this arrangement might suffer from one or more of the above-mentioned problems and hence does not lend itself to use in situations where reliability is important. It is an object of the present invention to provide a gas pressure regulator that overcomes or at least ameliorates one or more of the above discussed disadvantages of the prior art. According to a first aspect of the invention there is provided a pressure regulator for low pressure delivery of gases from a high pressure source, said regulator comprising: a gas inlet and a gas outlet defining a gas path therebetween; a regulating element disposed downstream of the inlet and remote from the gas path; valve means provided at the gas inlet; and heat exchanger means disposed to extend from said valve means and along at least a portion of the gas path; said regulating element being resiliently displaceable in response to gas pressure and including mechanically connected actuating means to operate the valve means at the gas inlet to thereby regulate the gas pressure at the gas outlet, characterised in that the regulating element is off-line with respect to the gas path. It should be noted that all references to gas inlet are to the gas formed at the inlet valve exit and not to the high pressure gas source. Desirably, the regulating element is disposed at a position that is also downstream of the gas outlet. Preferably the mechanical connection of the regulating element to the valve is adapted to increase the mechanical advantage, such that a lower rating regulating element may be used and the sensitivity of the regulator as a whole can be enhanced. In a preferred embodiment specifically designed for large scale use with liquifiable gas products such as CO 2 , a heater is provided at the gas inlet that also thermally isolates the regulating element. In smaller scale low flow rate applications the externally powered heater is replaced by a non-powered heat exchanger that works on heat transfer from external ambient temperature conditions. This heat exchange is required to prevent dry ice formation at the inlet by raising the delivery temperature of the gas, and simultaneously further thermally isolates the regulating element so that it is not subjected to the potentially harmful effects of low operating temperatures. Desirably, the regulating element is of the type comprising a chamber separated by a diaphragm to define an active pressurisable portion and an inactive portion. The diaphragm is displaceable by gas pressure against a spring of predetermined tension and is connected to the inlet valve via a mechanical linkage that increases the mechanical advantage, thereby also increasing the sensitivity of the regulator. In one embodiment, the regulating element comprises a modified proprietary gas regulator of the kind manufactured by the company REGO and identified as the LV4403SR and TR series. The units are modified by blocking the outlet and attaching an extended actuating arm to the linkage mechanism, such that the inlet valve of the regulator of the invention is external to and remote from the body of the regulating element. In a preferred embodiment for large scale use with liquifiable gases, the heater comprises a generally hollow body adapted to connect to the inlet of the regulalating element referred to above and receive the inlet valve and actuating means. The heater preferably has a plurality of peripherally spaced heater elements mounted in the wall of the hollow body. The heater unit also desirably includes a gas heating passage in the form of a long lenth of tubing coiled around the periphery of the heated hollow body that is in fluid flow communication with the inlet valve. In another embodiment more suited to low flow rate applications, the ambient temperature heater comprises a hollow, preferably finned body adapted for connection to the inlet of the regulating element and to receive the mechanically connected valve actuating means and inlet valve. The heater also includes an ambient temperature gas heating passage in the form of a long length of tubing coiled around the perifphery of the hollow body that is in fluid flow communication with the inlet valve. The inlet valve desirably comprises an inlet nozzle which is preferably disposed within the hollow portion of the heater unit at an end remote from the regulating element and which is operatively associated with the actuating arm of the regulating element linkage. The outlet of the inlet nozzle is in fluid flow communication with the external gas heating coiled tubing. According to a second aspect of the invention there is provided a gas distribution system for delivering gaseous fumigant from a high pressure source to a storage area at a low delivery pressure, said system comprising: a pressure regulator according to any one of claims 1 to 11 having a gas inlet adapted to receive gaseous fumigant from a high pressure source; and flow monitoring means connected to the gas outlet to monitor the flow rate of gas from the low pressure outlet to the storage area. Desirably, the high pressure source of gas is a pesticidal fumigant in the form of a pressurized storage cylinder containing a pesticide in a liquifiable gas base such as CO 2 . The cylinder is desirably connected with the inlet valve of the regulator via a suitable conduit. This conduit preferably includes a check valve at its end adapted for connection to the cylinder to prevent moisture entering the system after disconnection and a solenoid valve adjacent the regulator inlet valve to selectively cut of the supply. Pressure indicators and in-line filters may be incorporated into the conduit in the usual manner. It is further preferred that the distribution system includes a central control means such that it can be pre-programmed for automatic operation. In a preferred form, the system also includes means to detect the absence of gas flow which may, in one preferred embodiment, comprise a pressure differential switch disposed to measure the pressure difference across the gas heating passage. The pressure sensor for the inlet may be disposed in the active chamber portion of the remote regulating element. It will be clear that the regulator according to the invention has many advantages over the prior art. For example, by placing the regulating element off-line with heat exchanger means associated with the gas path, the element itself need not be capable of being able to withstand the extreme variations in temperature as would be required by most conventional in-line regulators. It has also been possible to provide a regulator that uses a relatively large diaphragm compared to that of the prior art, making the device generally more sensitive and stable. Two preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a gas distribution system incorporating a first embodiment pressure regulator according to the invention; Figure 2 is an enlarged sectional view of the pressure regulator shown in Figure 1; Figure 3 is a schematic side view of a second embodiment pressure regulator according to the invention; and Figure 4 is a schematic plan view of the regulator shown in Figure 3. Referring first to Figures 1 and 2 of the drawings, the pressure regulator 1 can be seen to include a gas inlet 2 and a gas outlet 3, defining therebetween a gas path illustrated by arrows 4. A regulating element shown generally at 5 is provided at a position remote and downstream from the gas inlet 2 so as to effectively be off-line from the gas path 4. The regulating element 5 is mechanically connected to operate a valve 6 at the inlet 2 by means of an extended actuating arm 7. The regulating element 5 includes a body 13 separated by a diaphragm 8 to define an active chamber portion 13a and inactive portion 13b. The diaphragm is displaceable by gas pressure against a spring 9 of predetermined tension located in the inactive chamber 13b. The spring tension can be varied to adjust the regulator setting and thus the pressure reduction achieved. The diaphragm 8 is connected to the inlet valve 6 by the actuating arm 7 which extends from a mechanism shown generally at 10 that serves to increase the mechanical advantage between the diaphragm 8 and the inlet valve 6. In this preferred embodiment the inlet valve 6 includes an inlet nozzle 11, the outlet to which is opened and closed by means of the stem tip 12 attached to the distal end of the actuating arm 7. In the embodiment described, the regulating element is a modified regulator of the kind manufactured by the company REGO and identified as the LV4403SR and TR series. The selected REGO regulator has a 5-35kPa or 35-70kPa rating. The diaphragm is approximately 100 mm in diameter and the mechanism 10 is a pivoted linkage that provides a reduction ratio of approximately 5:1. This serves to convert a coarse deflection of the diaphragm in the illustrated vertical direction, to a fine axial movement of the actuating arm 7 and stem tip 12 toward and away from the inlet nozzle 11, with a corresponding increase in the force applied. For the application illustrated a nozzle having an outlet diameter of approximately 1mm is preferred. The regulating element also includes a pressure relief valve 14. Disposed around the inlet valve 6 at the gas inlet 2 and along the gas path 4 to the regulating element 5 are heat exchanger means in the form of a heater unit shown generally at 15. This heater includes a generally cylindrical hollow body 16 adapted for connection to an inlet 17 of the regulating element 5 by means of a threaded connection shown at 18. The heater 15 also includes a plurality of circumferentially spaced longitudinally extending heating elements 19, mounted in the wall 20 of the hollow body 16. A gas heating passage shown generally at 21 is provided in the form of a long length of tubing 22 coiled around the periphery 23 of the heated body 16. In the embodiment described a tubing length of about 2.5m is used. The heater 15 is arranged such that the inlet valve 6 is disposed within the hollow portion 24 of the heater 15 at an end 25 remote from the regulating element. The outlet of the valve 6 is placed in fluid flow communication with the coiled tubing 22 by means of an interconnecting passage 26. When used in a gaseous fumigant distribution system as shown as Figure 1, the gas inlet 2 of the pressure regulator 1 is connected via a conduit 30 to a high pressure source of pesticide in a liquified CO 2 base stored in cylinder 31. The conduit 30 preferably includes a check valve 32 at its end adapted for connection to the cylinder 31. The check valve may comprise a Shrader* type valve. This valve is used primarily to prevent air and moisture from entering the line after disconnection of the conduit from the cylinder. The conduit 30 may also include an in-line filter 33 and a pressure indicator 34 as illustrated. A solenoid valve 35 and flow indicating system 36 are also provided in the line 37 to the storage area of the silo to which the fumigant is to be delivered. Pressure sensors 44 are located at the inside of the regulator and outside of the heater tube 22 and connected to a pressure differential switch 45. The pressure sensor detecting the pressure inside the regulator is conveniently located in the active chamber portion of the regulating element 5. The pressure differential switch 45 and electrical connections to the heater elements 19 are all connected to a central control panel 50. In use, the gas mixture in cylinder 31, which is stored at a pressure of the order of 5 MPa, is delivered to the inlet valve 6. Gas admitted through the valve 6 is passed around the actuating arm 7 and linkage 10 into the active chamber 13a of the regulating element 5. The spring 9 of the regulating element 5 acts on diaphragm 8 to force the diaphragm downward such that the valve 6 is biased in an inoperative condition into the open position. As the gas admitted to chamber 13a exerts pressure on the underside of the diaphragm 8 against the action of the spring, the stem tip 12 is forceably driven against the inlet nozzle 11 to thereby control the pressure of the gas delivered to the gas outlet 3. The pressure differential switch 45 monitors the pressure difference across the pressure regulator between the gas inlet, which is the same as the active chamber 13a of the regulating element, and the gas outlet. This is equivalent to the pressure difference across the respective ends of the coiled tube 22. Under normal operating conditions when there is gas flow, there should be a small pressure drop of the order of 50Pa-68kPa due to pressure loses in the tubing 22 of the heater unit 15. When there is no flow however, the pressure equalises and the no-flow condition is thereby detected. The heater unit 15 is adapted to maintain a temperature within the heater adjacent the gas inlet of around 25°C. This is sufficient to ensure that no dry ice forms and that the regulating element 5 is not subjected to the potentially damaging effects of low temperature operating conditions. This is particularly important with CO 2 as it will naturally cool on release from the cylinder to temperatures as low as -80°C. Referring next to Figures 3 and 4 there is shown an alternate second embodiment low flow rate regulator according to the invention and where appropriate like reference numerals have been used to denote corresponding features. In this second embodiment, the heat exchange 15 does not have any heating elements 19 (see previous Figures) but instead has a plurality of external fins 27 that transfer ambient heat to the sub-ambient gas in the tubing 22. The internal workings of the device are otherwise essentially the same as that described in reference to Figures 1 and 2. It will be appreciated that the regulator of the invention provides a sensitive and accurate pressure regulation, which means a correspondingly sensitive and accurate control of gas flow. Furthermore, the regulator of the invention is capable of pressure reductions of up to approximately 50,000:1 or even approximately 100,000:1 depending on: the size of the regulating element used; the mechanical advantage conferred by the linkage mechanism 10; and the size of the inlet nozzle 11. The regulator according to the invention is also highly resistant to contamination in comparison to prior art flow regulating devices, particularly those using needle valve restrictors or other control valves and the like. In the event that there is a build-up of contamination with the regulator of the invention, the resulting pressure reduction caused by the blockage serves to open the inlet valve which momentarily admits high pressure gas into the valve thereby automatically cleaning the valve seat. Similar contamination would build up and block a prior art needle valve type device. Whilst a regulating element of a diaphragm type construction has been illustrated, a piston type regulator or other regulating mechanism could be employed in a similar manner. Although the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art, that the invention may be embodied in many other forms.

Claims: A pressure regulator (1) for low pressure delivery of gases from a high pressure source, comprising a gas inlet (2) and a gas outlet (3) defining a gas path (4) therebetween; a regulating element (5) disposed downstream of the inlet (2) and remote from the gas path (4); valve means (6) provided at the gas inlet (2); and heat exchanger means (15) disposed to extend from said valve means (6) and along at least a portion of the gas path (4); said regulating element (5) being resiliently displaceable in response to gas pressure and including mechanically connected actuating means to operate the valve means (6) at the gas inlet (2) to thereby regulate the gas pressure at the gas outlet (3),characterised in that the regulating element (5) is off-line with respect to the gas path. A pressure regulator (1) according to claim 1 characterised in that the heat exchanger means (15) extends from at least the gas inlet (2) to the regulating element (5). A pressure regulator according to claim 1 or claim 2 characterised in that the gas inlet valve (6) is disposed within the heat exchanger means (15). A pressure regulator according to any one of the preceding claims characterised in that the mechanical connection (7) of the regulating element (5) to the inlet valve (6) is adapted to increase the mechanical advantage therebetween such that a coarse deflection of the regulating element (5) is converted to a fine movement at the inlet valve (6) with a corresponding increase in the force applied thereto. A pressure regulator according to any one of the claims characterised in that the heat exchanger means (15) comprises a heater having a generally hollow body (16) adapted to connect to the regulating element (5) and receive the mechanically connected valve actuating means and inlet valve (6), one or more externally powered heater elements (19) mounted in the wall of the hollow body (16), and a gas heating passage (21) in the form of a long length of tubing (22) coiled around the periphery of the heated hollow body (16) that is in fluid flow communication with the inlet valve (6). A pressure regulator according to any one of claims 1 to 4 characterised in that the heat exchanger means (15) comprises a non-powered ambient heater having a hollow body (16) adapted to connect to the inlet of the regulating element (5) and receive the mechanically connected valve actuating means and inlet valve (6), and an ambient temperature gas heating passage (21) in the form of a long length of tubing (22) coiled around the periphery of the hollow body (16) that is in fluid flow communication with the inlet valve (6). A pressure regulator according to claim 6 characterised in that the heat exchanger means (15) includes external fins (27) adapted to exchange heat with the adjacent ambient air. A pressure regulator according to any one of claims 5 to 7 characterised in that the inlet valve (6) comprises an inlet nozzle (2) disposed within the hollow portion (16) of the heater and which is operatively associated with an actuating arm (7) of the mechanically connected regulating element linkage, the outlet of the inlet nozzle (2) being in fluid flow communication with the gas heating passage (16). A pressure regulator according to any one of the preceding claims characterised in that the regulating element (5) is of the type comprising a chamber separated by a diaphragm (8) to define an active pressurisable portion and an inactive portion, the diaphragm (8) being displaceable by gas pressure against a spring (9) of predetermined tension, the diaphragm (8) being connected to the inlet valve (6) via a mechanical linkage (7) that increases the mechanical advantage to increase the sensitivity of the regulator (5). A pressure regulator according to claim 9 characterised in that the regulating element (5) comprises a modified proprietary gas regulator of the kind manufactured by the company REGO and identified as the LV4403SR and TR series. A gas distribution system for delivering gaseous fumigant from a high pressure source (31) to a storage area at a low delivery pressure, said system comprising: a pressure regulator (1) according to any one of claims 1 to 10 having a gas inlet (2) adapted to receive gaseous fumigant from a high pressure source (31); and flow monitoring means (36) connected to the gas outlet (3) to monitor the flow rate of gas from the low pressure outlet to the storage area. A gas distribution system according to claim 11 characterised in that the high pressure source (31) of gas is in the form a of pressurised storage cylinder containing a fumigant in a liquifiable gas base. A gas distribution system according to any one of claims 11 to 12 characterised by a central control means such that the system can be pre-programmed for automatic operation. A gas distribution system according to any one of the preceding claims characterised by a pressure differential switch (45) disposed to measure the pressure difference between the gas inlet and the gas outlet of the regulator to detect the presence of absence of gas flow.

Inventors: SCHONSTEIN DAVID, SHORE WILLIAM, SCHONSTEIN, DAVID, SHORE, WILLIAM
Applicants: COMMW IND GASES, THE COMMONWEALTH INDUSTRIAL GASES LIMITED
Application year: 1994
Main classification: F17C7
IPC codes: F17C7, G05D16, F17C13